The present invention relates to an image forming method wherein image data corresponding to one selected pixel portion or to u.times.v (horizontal.times.vertical) pixels portion are formed with small dots in a quantity equal to n.times.m (horizontal.times.vertical) dots, and these small dots are modulated by reference wave signals or the like to be modulated signals which are dot-recorded or dot-displayed for reproducing line images and half tone images.
In the field of an image forming apparatus based on an electrophotography, an image on an original is read as image signals by a scanner, and the image signals are subjected to gradation correction, A/D conversion and shading correction to be image density data. The image density data are modulated by reference wave signals so that digital images having therein reproduced half tone images may be obtained.
With regard to image signals obtained by reading an image on a original by a scanner, an edge portion of the image is read as a half tone image density due to an aperture of a solid image sensor incorporated in the scanner. When image density data obtained from the image signals is used to produce a latent image on a photoreceptor, recording pixels corresponding to edges of the latent image are recorded on an average within recording pixels when density is medium. Therefore, sharpness of the image is deteriorated for recording. To correct this problem, MTF correction methods can be used wherein a differential filter or a Laplacian filter is used for image signals for sharpening images. In these methods, however, only edge portions of an image are sharpened and uniformity of halftone images is relatively deteriorated.
Even when interpolation characters or graphics are formed by CG or font data, on the other hand, the same problem still happens. Namely, when interpolation data interpolate edge portions smoothly by means of medium density, recording pixels corresponding to the edge portions are recorded in pixels as the average density. Therefore, the sharpness of recorded images is deteriorated.
For the above reason, medium density processing that works effectively on the edge portions of an image is required.